Power,synchronizing and timing waveform generator and apparatus

April 15, 1969

POWER,

Filed Jan. 12, 1966

k. e. perry 3,439,338

SYNCHRONIZING AND TIMING WAVEFORM GENERATOR AND APPARATUS

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ATTORNEYS

April 15, 1969 κ. e. perry 3,439,338

POWER, SYNCHRONIZING AND TIMING WAVEFORM

GENERATOR AND APPARATUS Sheet % of 2

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ATTORNEYS

United States Patent Office

3,439,338

Patented Apr. IS, 1969

439 338

POWER, SYNCHRONIZING AND TIMING WAVEFORM GENERATOR AND APPARATUS

Kenneth E. Perry, Wayland, Mass., assignor, by mesne assignments, to EG &amp; G International, Inc., Bedford, Mass., a corporation of Delaware

Filed Jan. 12,1966, Ser. No. 520,203 Int. Cl. H04g 1/18; H04m 11/04

U.S. Cl. 340—147 7 Claims

ABSTRACT OF THE DISCLOSURE

A system for remote control over distribution transmission lines is disclosed. Periodic time variations in signals of special waveform provide synchronization and timing at the remote station.

The present invention relates to power, synchronizing and timing apparatus, being more particularly directed to the generation of alternating-current energy for transmission along distribution transmission lines such as, for example, underwater cables connected with pluralities of measuring or other instruments and equipment, or other electrical distribution systems and the like.

Numerous types of synchronizing and power current or voltage generators have been used to transmit energy suitable for operating electrical and electronic apparatus and for insuring the proper synchronization or timing of such operation. Such synchronization has been attained with the aid of periodic synchronizing signals that are distinct from the signals being transmitted in amplitude, frequency or phase. In certain applications, however, as in transmission along underwater cables associated with electrical instruments distributed therealong, and similar systems, the signal amplitude may vary along the cable in an unknown manner due to unpredictable underwater attenuation and other losses, rendering the use of amplitude-variation synchronization unreliable. Frequency or phase modulations or changes for purposes of providing a synchronizing signal are similarly subject to disadvantages residing in the requirement for channel separation filters and other complex and costly equipment.

In accordance with the present invention, therefore, in summary, synchronization and timing are effected by periodic time variations in a train of signals of special waveforms and other characteristics particularly suited to the unusual problems of the power, synchronization and timing requirements of cable-fed and supported underwater instruments and similar systems.

A further object of the invention is to provide a novel power, synchronization and timing system of more general utility, also.

Other and further objects will be pointed hereinafter and will be more particularly set forth in the appended claims.

The invention will now be described in connection with the illustrative example of such underwater systems with reference to the accompanying drawings, FIG. 1 of which is a combined schematic and block diagram of a preferred embodiment;

FIGS. 2A and 21 are explanatory amplitude versus time graphs illustrating the waveforms at various portions of the circuit of FIG. 1; and

FIG. 3 is a schematic circuit diagram of a preferred power amplifier for use in the system of FIG. 1.

Referring to FIG. 1, a square wave generator of any conventional form is shown at 2 applying its output at K (the train of impulses of FIG. 2A), to one input of an “and” gate 4, the other input K₉ of which is applied from a later-described first flip-flop stage FFj. The pulses may, for example, be of sixty cycle frequency or any other desired frequency. The output of gate 4 is applied at K_xto a counter 6, shown for illustrative purposes as having successive flip-flop stages FF₂, FF₃ . . . FF₄, the respective outputs of which are derived at A-A', B-B', . . . C-C'. The output C of counter flip-flop FF₄ is applied at 8 to the “0” input of the first-mentioned flip-flop FFi, and the output K_t of the square-wave generator 2 is applied at 8' to the “1” input of FF₄. The successively divided outputs at A, B and C of respective counter flipflop stages FF₂, FF₃ . . . FF₄ are respectively shown in waveforms FIGS. 2B, 2C and 2D, such that after a predetermined number of impulses are counted from the generator 2, FIG. 2A, the flip-flop ΡΡ₄ is caused to generate the impulse I of FIG. 2E which, as before stated, is applied to the gate 4 together with the signal train of square wave impulses at Κ₄. There thus results at the output K_x of gate 4, the waveform of FIG. 2F, having a distinctive wider pulse at I' which, in this illustrative example, is three times the width of each negative pulse of FIG. 2A.

The complementary outputs A', B' and C' of counter flip-flops FF₂, FF₃ and FF₄ are shown fed to gate 10, the output Z&gt;_z of which has the waveform of FIG. 2G; namely, a positive pulse I four times the width of each positive or negative pulse of the original train of FIG. 2A or twice the width of each combined positive and negative pulse cycle of FIG. 2A. The output b_z is applied at 12 to a further gate 14 to which is also fed, at 12', the output K₉ (FIG. 2E) from flip-flop FFi· The output b₂ is also fed to an inverter 16 and thence to a similar gate 14' also energized by the original impulse train of FIG. 2A from output K₄ via conductor 18. The combined output T_c of gates 14 and 14' has the waveform of FIG. 2H, providing a positive-negative square-wave cycle Γ of twice the period (or half the frequency) of the preceding and following trains P and P' of square-wave impulses.

In accordance with a preferred embodiment of the invention, the square-wave trains P and P' preceding and following the double-period cycle Γ in the output T_oare rendered substantially sinusoidal substantially to eliminate higher harmonics that not only introduce substantial cross-talk when transmitted along, for example, underwater cable II for the purposes before discussed, but introduce ringing effects as well. These substantially cross-talk-free and ringing-free results could not be obtained with the higher-harmonic-containing square-wave impulses of FIG. 2H. This conversion to the substantially sinosoidal narrow-band waveforms at S and S', FIG. 21, is effected with a low-pass filter 20, substantially eliminating harmonic frequencies above, say, the third harmonic of the fundamental frequency of the waveform S, and preferably attenuating such third harmonic as well. The double period or double wave-length cycle (2X) shown at I, FIG. 21, will, however, be considerably flattopped, as shown, for advantageous reasons later explained. It is of course to be understood that the particular waveform produced at T_c' is periodically repeated, having similar substantially sinusoidal alternating current waveform trains S, S' of predetermined amplitude and predetermined wavelength λ, each interconnected by a substantially flat-topped cycle I (or plural flat-topped impulses, all generically herein termed “cycle”), of substantially the said peak amplitude but twice the wavelength (or, if desired other multiples than two), substantially symmetrical with respect to the zero current time axis shown as a horizontal dotted axis in FIG. 21.

Through the use of this special waveform current at

T_c', a combined power, synchronization and timing signal is provided for transmission, preferably after amplification at 22, along transmission lines TL₄, associated with the cable II. At various locations along the cable II, instruments or other electrical apparatus, such as the

3,439,338 elements 24 and 24', are coupled to the line TL, and supported in well known manner from the cable. In view of the nature of the waveform of FIG. 21, this coupling may be inductive, as through transformer T of instrument 24, or of any other type including direct coupling. The distinctive cycles I may be used for timing and synchronizing purposes (controlled, for example, by the zero crossing of the positive portion of I) by the synchronizing input 26 of the instrument or other device 24. If the instrument embodies one or more sensors (for detecting such underwater phenomena, for example, as water current, speed and direction, temperature or pressure and the like), the sensed signals may be digitized at 30, as is well known, and transmitted back up the cable II via line TL₂, at times determined by such synchronizing. The same waveform of FIG. 21, moreover, supplies current for rectification in the instrument power supply 28 to operate the instrument circuits and apparatus.

Improved power amplification efficiency may be obtained through the flat-topped waveform above-discussed, with a power amplifier circuit 22 of the type shown in FIG. 3, embodying a complementary pair of emitterfollower power transistor relays Q, and Q₂. Such transistors then operate most of the time in saturation conduction with little voltage drop, so that little dissipation occurs and improved efficiency results.